In the rise of modern scientific philosophy, one can distinguish four general periods. Its early phase is part of the intellectual history of 19th-century Austria-Hungary. Second, we find it reaching its self-confident form in the 1920s and early "30s, chiefly in the collaborative achievements of the Vienna Circle and its analogous groups in Prague, Berlin, Lwow and Warsaw. Third is the period of its further growth and accommodation during the period roughly from the late 1930s to about 1960, especially in the U.S.A., as mediated largely by the European refugees from fascism. Lastly, the movement's fate from the 1960s on may be understood as its integration with, or dissolution into, other related modern streams.